me and some friends had a debate last night, i hear different things, id like to know the real truth behind it. do turbos and vtec go good together, pro's and cons please

 

no. vtec is not good for boost.

vtec heads flow better than non-vtec heads however.
i have gone through this debate numerous times, and i will always remain by my statement that vtec is not good for boost. Sure, when you arent boosting much, it doesnt really matter, vtec motors get higher numbers per pound of boost because of the fact that a vtec head flows better than a non-vtec head.

Most big drag race teams have disconnected the vtec solenoid etc, the cams are really agressive and dont include vtec, because when you are putting a lot of boost into the cylinder you dont want to have exhaust valves open for long bedcause the boost will go out the tail pipe which would mean for a loss in power.

You gotta look back on it, honda motors are pretty gutless, and they want to rev trhem high, they need a method to keep the power coming as the rpms go up. So why not put more a/f mix into the cylinder for a bigger burn, hence vtec is sort of like boost, but not really.

vtec, in the long run, is not good for boost at all, period.

 

This needs a bit of clarification. The more aggresive cams are, the more overlap they are going to have by default, Vtec or not. Overlap is the cause of blowby which is the power-robber that you referred to. The purpose of Vtec is to have the advantages of a large-profile lobe at the higher RPM range & a smaller-profile lobe for the lower RPM range. If the car is turbo'd, this is not needed as torque is generally increased significantly over the entire rev-range once boost builds. Also, with the increased stresses a turbo puts on an engine, you generally don't want to spin it as tight as you would an NA car.

So it's really more a matter of necessity than anything else. Vtec is just not "needed" in a boosted engine as much as it is in a non-boosted one. However, the reality of it is this; if you have cam gears that allow you to dial out the overlap provided by the Vtec lobe, blowby is not a problem & Vtec cams are workable.

 

but by doing so you are basically disabling vtec, so ultimately vtec is worthless for boost, and more of a pain in the *** to get by instead of a helping factor.

 

If you are referring to reducing overlap as disabling Vtec, you are incorrect. The larger Vtec lobe will engage regardless of the amount of overlap dialed out by cam gears. It's just that you WANT overlap in an NA app, but NOT a boosted one.

 

contrary to what there saying
vtec will kick major *** on a turbo.
it just needs more fuel and tuning.

 

Only if you have adjustable cam gears to tune with.

 

not true
with proper igition timing, you dont need to play with the cam gears as much
or you can throw gsr cams in (less agressive, and more mid powerband based) and not need to touch it.

 

Key words here being "need" and "as much".

No, you don't NEED to adjust the cams at all, on any application. But it's something you want to do for optimum power - especially on a boosted app. The amount of adjustment you'll want to do depends on the amount of boost you're pushing, and as you stated, the cams. Granted, with smaller cams & lower levels of boost, blowby wouldn't be nearly as significant as with larger cams and/or higher levels of boost, thus necessitating less cam adjustment for optimum performance.

 

so is it better just to turbo something like an LS thats nonvtec or something with like an si or gsr, or hell a lude.

 

this is waht my friend tells me..

actually Aunie, you are 100% wrong...vtec is perfectly fine to run with turbo's when you hear people talking bad about it, is because of the lag....well that is because it is people that are used to having vtec in the first place, those people without it never knew what it felt like in the first place...Having vtec inabled just gives you that much more power then boost finally hits. And as for the valves staying open...that is the whole reason why companies like Crower and Skunk2 create turbo cams for cars with vtec....it's harder to tune a car that still has vtec inabled, so most people don't mess with it, but the advantages of having it still are hugely there if you have someone who knows what the heck they are doing.

 

hhhhmmm, some good info again from fellow h-t memebers.

now, which can outrun which?can an ls or b20 turbo outrun ls or b20 hybrids at 1/4 mile? jus wonderin' guys